Electric-circuit breaker and the like



Aug. 18, 1925. 1,550,209

H. w. CLOTHIER ET AL ELECTRIC CIRCUIT BREAKER AND THE LIKE .Filed March 11. 1924 3 Sheets-Sheet l "Mu. Hm,

Aug. 18, 1925-. 1,550,209

H. W. CLOTFHER ET AL LECTRIC CIRCUIT BR AKER AND THE LIKE Filed March 11, 1924 3 Sheets-Sheet 2 Au 1s,"1925.- 1,550,209

H. W. CLOTHIER ET AL ELECTRIC CIRCUIT BREAKER AND THE LIKE Filed March '11. 1924 3 Sheets-Sheet 3 Patented Aug. 18, 1925.

UNITED STATES PATENT OFFICE.

HENRY WILLIAM CLOTHIER, OF WALL-SEND-ON-TYNE, AND BRUCE HAMER LEESON, OF TYNEMOUTH, ENGLAND, ASSIGNORS TO A. REYROLLE & COMPANY LIMITED, 0F HEIBBURN-ON-TYNE, ENGLAND, A COMPANY REGISTERED UNDER THE LAWS OF GREAT BRITAIN.

ELECTRIC-CIRCUIT BREAKER AND THE LIKE.

Application filed March 11, 1924. Serial No. 698,503.

To all whom it may concern:

Be it known that we, HENRY ILLIAM CLOTHIER and BRUCE HAMER LnnsoN, subjects of the King of England, and residing respectively, at lVallsend-on-Tyne, county 0 Northumberland, in England, and Tynemouth, county of Northumberland, in England, have invented certain new and useful Improvements in Electric-Circuit Breakers and the like, of which the following is a specification.

This invention relates to electric circuit breakers and the like and has particular reference to circuit breakers suitable for use on traction or other systems where short circuits are likely to occur. Such short circuits, as is well known frequently cause flash-overs on the commutators of direct current generators. The short circuit current probably first produces a conducting vapour on the commutator the quantity of this vapour being a function of the current and of the duration of that current- Thus to prevent these flash-overs the circuit breaker employed should keep the short circuit current low and break the circuit quickly.

These conditions are fulfilled in a circuit breaker according to this invention which is furnished with series and shunt windings, the series winding tending toopen the contacts and the shunt winding to keep them closed. Preferably the windings are on separate magnetic circuits and act on a movable armature common to both circuits, the series coils carrying the main current and the shunt coils being connected say across the terminals of the D. C. generator. Under normal load conditions the shunt coil and its core act as a holding electromagnet and retain the armature in such a position as tokeep the contacts closed. This retaining or holding action is against the force exerted by the series coils and also preferably against the action of auxiliary springs which tend to open the contacts.

lVhen a short circuit occurs the voltage across the shunt coil drops and the holding electromagnet releases the armature. At the same time the current in the series coil rises and exerts an increased pull on the armature. As the armature moves away from the shunt wound magnet, the force exerted by that magnet will decrease as the square of the distance between the armature and the magnet pole. Further the pull due to the series magnet will increase in the same proportion for constant current but also, as above mentioned the current is increasing in the series coils and, depending to some extent on the density of flux in the iron, the pull due to the series coils will increase in proportion to the square of the current. It will thus be seen that the opening action of the circuit breaker is very rapid.

There is also another important effect. As above mentioned the movable armature is common to the two magnetic circuits and the poles of the two electron'iagnets are so arranged that the fluxes through the armature are in the same direction. Now before the armature moves the flux in it due to the shunt winding will decrease as soon as the voltage drops. This has the effect of increasing the flux due to the series coils or in other words of introducing reactance into the series circuit. The importance of this feature is due to the fact that the reactance introduced retards the growth of the short circuit current in its first stages, i. e., before the mechanical operation of the breaker begins. In other words the initial slope or steepness of the current-time curve of the short circuit current is reduced and time is given for the mechanical portions of the mechanism to accelerate and open the contacts before the short circuit current reaches the maximum value which it would otherwise have attained.

In the accompanying drawings Figure 1 is a front view showing diagrammatically the essential parts of one construction of circuit breaker according to this invention, and

Figure 2 is a side view.

Figure 3 is a diagram showing by way of example how the improved circuit breaker may be used on a system supplying power for traction purposes.

With reference first to Figures 1 and 2. In a suitable framework (not shown in the drawings) two magnetic cores A and B are supported, the poles of the two Us being separated by a gap in which a more or less rectangular armature C can move up and downthe armature thus being capable of the lower core B when. thearmature is in its bottom position as shown in the figures.

'lhe upper magnetiocore A carriesthe serice-winding Dand the lower magnetic core Bis excited by a-shunt -or potential winding E. The uppermember or yoke of the core Ais divided and in the gap the main con-. tacts F and F are'placed. These contacts maybe ot' any suitable form but are pref-- erably provided with main and sparking contacts F F of the hint described in-the specification of British Letters Patent No. 16?;86. Convenientlythe main contactF. is fixed and the othermain contact F' is mounted on a spindle G which can-be rocked to open the contacts. It will be'understood that the object'ot placing thesecontaots in a gap-in theuppermagnetic circuit is to cause the opening of the contacts totake placein a strong magnetic field whichtends to blow out the-arc'between the sparkingcontacts;

The rocking of thespindle Gcarry-ingthe movable contact F is broughtabout by means of links or connectingrods H joined between crank, arms-H on the spindle G and arnisG fixed to the arn'iature C. These rods-or links H areprovided w-ith springs H which tend to keep the armature 0 against the poles ofthe series magnet core A in which positionthe-contacts would be open as indicated in chain-lines in Figure Preferably a dash-potC is provided to relieve the mechanical shock due-to the high velocity otthe armature and its connected parts.

The shunt or potential winding Ben the lower or holding magnet core B may bein two or more parts or maybe'tapped and connectedto a switcharm or rheostat so that the current in the windingE maybe regulated. Asshown inFigure-Q this regulation is effected by a switch arm- J controlling a stepped resistance J in series with the winding E. An additional coilmay-be provided on this shunt or holding magnet B, this winding being. indicated atzE. This additional. winding E may be used to close the contacts, that is to say, to pull the arma. ture down on to the magnet-core B after it has been raised to open thecontacts.

Although the. improved apparatus is terineda contactbreaker and'is adapted for use. as such, it istobe undertsood thatmthe separation of the contacts F F" need. not necessarily break the circuitentirely. The

apparatus may function for instance as a current diverter rather than a circuit-breaker. This may be provided for by joining a limiting resistance Kacross, the contacts F andF' as. shown diagrammatically in. Figure 2. This resistance K may be graded'or stepped and may be controlled by asWitchK operated by the movement of the armature G. Such an arrangementis useful when the improved circuit breaker is employed in conjunction with some known form of switch or circuit breaker operating comparatively slowly. When thus employed the high speed circuit breaker according to'this invention does not finally break the circuit but it takes the stress produced-by theshort circuit current, it-retards the growth of that current and protects the generator and then when the gradedlimiting resistance above referred'to is employed it cuts out the current progressively before thecirc-uit is finallyinterruptedby the trip mechanism of an ordinary circuit breaker.

l he*diagram forming Figure 3 is merely given to show by way of example how the improved circuit breaker or-- current diverter may be-used i'nconnection with asystom supplying current i'ortraction purposes. In this. diagram L L" are the busbais, M is arotary or motor generator which isto be proteeted by the-circuit breaker and N and-l\ representthe' track and live rail respectively. Those parts of the circuit breaker or current diverter which are-shown in- Figure 8 are lettered to correspond with the corresponding parts in Figures land 2. lirFigure- 3, O is an-ordinary slow speed circuit breaker controlling the main connection to the bus-bar L and P is a. slow-speed feeder cirouit breaker controlling. the: connect-ionirom the bus-bar L tothe live rail N but providedwith auxiliary contactsl which-control the closing coil-E ofthe oilc-uit-breaker or current diverteix In this-a1 rangenlent themain contactsF- F of the cir. cuit breaker areclosed automatically. by the action of the coilsE'and E as soon as the feedeiv circuit: breaker P has opened the faulty feeder which it controls, provided that the Voltage. o't thegenerator 1W has risen again to the normal.

Referring again'to- Figures 1 andEZ it isto be understood that :the winding of the series coild) and the potential coil E is such that the flux from the core A; tendsto pass through thearmature C in the same direction-as the fluxyfrom thecore B. Thussupposing the armature G to be held down by theholding orpotential. coilE as shown in the figures,- then a weakening of the flux from the core B due to adecrease of current in the winding E will: cause. or. allowtan increase. ofthe flux: in the core: A. This in? creases the reactance of the series winding D: and. tends to retard the growth of the current in that winding due to a short circuit or overload.

Although in Figure 2 the graded resistance K across the main contacts F F is shown as controlled directly by a switch arm moved by the armature, it is 'to be under stood that the movement of the armature may control this graded resistance indirectly through appropriate circuits with local contact makers.

What we claim as our invention and desire to secure by Letters Patent is 1. In an electromagnetic circuit-controlling device, the combination of two magnetic cores or circuits, an armature movable in a gap between such cores, a switch operated by the movement of the armature, a series winding on one magnetic core tending to move the armature so as to open the switch, and a shunt winding on the other" magnetic core tending to hold the armature so as to keep the switch closed, the series and shunt windings being so arranged that the magnetic fluxes due to currents in them pass through the armature in the same direction so that weakening of the flux due to a decrease of current in the shunt winding causes an increase of the flux in the magnetic circuit of the series winding and consequently increases the reactance of that winding and tends to retard the growth of the current in that winding due to a short circuit or overload.

2. In an electromagnetic, circuit-controlling device, the combination of two U- shaped magnetic cores having their similar poles separated by an air gap, one of such cores having a second air gap in its yoke, an armature movable in the air gap between the poles, a switch operated by the movement of the armature, a series winding on the U-shaped core which is provided with the second air gap, said winding having sufficient ampere-turns to overcome the reluctance of said air gap and move the armature to open the switch where an overload occurs, and a shunt winding on the other magnetic core tending to hold the armature so as to keep the switch closed.

3. In an electromagnetic circuit-controlling device, the combination of two U-shaped magnetic cores having their similar poles separated by an air gap, one of such cores having'a second air gap in its yoke, an arma ture movable in the air gap between the poles, a switch placed in the second air gap and operated by the movement of the armature, a series winding on the U-shaped core which is provided with the second air gap, said winding having sufiicient ampere-turns to overcome the reluctance of said air gap and move the armature to open the switch where an overload occurs, and a shunt winding on the other magnetic core tending to hold the armature so as to keep the switch closed.

4. In an electromagnetic circuit-controlling device, the combination of two U- shaped magnetic cores having their similar poles separated by an air gap, one of such cores having a second air gap in its yoke, an armature movable in the air gap between the poles, a switch placed in the second gap and operated by the movement of the armature, a limiting resistance across the contacts of said switch, a series winding on the U-shaped core which is provided with the second air gap, said winding having sufiicient ampere-turns to overcome the reluctance of said air gap and move the armature to open the switch where an overload occurs, and a shunt winding on the other magnetic core tending to hold the armature so as to keep the switch closed.

5. In an electromagnetic circuit-controlling device, the combination of two U- shaped magnetic cores having their similar poles separated by an air gap, one of such cores having a second air gap in its yoke, an armature movable in the air gap between the poles, a switch operated by the movement of the armature, a series winding on the U-shaped core which is provided with the second air gap, said winding having sufficient ampere-turns to overcome the reluctance of said air gap and move the armature to open the switch where an overload occurs, a shunt winding on the other magnetic core tending to hold the armature so as to keep the switch closed and a regulating resistance and switch in said shunt winding.

6. In an electromagnetic circuit-controlling device, the combination of two magnetic cores or circuits, an armature movable in a gap between such cores, a switch oper ated by the movement of the armature, a series winding on one magnetic core tending to move the armature so as to open the switch, a shunt winding on the other magnetic core tending to hold the armature so as to keep the switch closed, and an additional winding on the shunt-wound magnetic core for use in moving the armature back after it has been moved by the. action of the series winding.

In testimony whereof we have signed our names to this specification.

HENRY IVILLIAM CLOTHIER. BRUCE I-IAMER LEESON. 

